Synchronization System and Method for Achieving Low Power Battery Operation of a Vehicle Locating Unit in a Stolen Vehicle Recovery System Which Receives Periodic Transmissions

1. A system for maintaining synchronization with a periodic transmission from one of a plurality of transmission sources while achieving low power battery operation of a vehicle locating unit in a stolen vehicle recovery system, the periodic transmission occurring during a transmission cycle period and including an expected message that has a transmission duration, the system comprising: a selectively-actuatable radio receiver for receiving during periods of actuation the periodic transmissions from the one of a plurality of transmission sources; and a microprocessor configured to look for a synchronization symbol in the expected message and to synchronize subsequent actuation of the radio receiver using the synchronization symbol; to reacquire a warm start synchronization if synchronization is lost; and to acquire a cold start synchronization if the warm start synchronization fails to reacquire synchronization.

2. The system of claim 1 , wherein the plurality of transmission sources includes a number of phased transmission sources.

3. The system of claim 2 , wherein, during the transmission cycle period, each phased transmission source of the number of phased transmission sources transmits a burst that has a burst duration and that includes a plurality of message indexes.

4. The system of claim 1 , wherein reacquiring warm start synchronization includes further adapting the microprocessor to: re-check for synchronization a predetermined number of times; and, if synchronization is not detected, to look for a synchronization symbol after waiting for a length of time.

5. The system of claim 4 , wherein if synchronization is not detected after rechecking for the predetermined number of times, the microprocessor is adapted to acquire the cold start synchronization.

6. The system of claim 4 , wherein warm start synchronization fails to reacquire synchronization if, after the predetermined number of times, loss of synchronization remains.

7. The system of claim 4 , wherein the length of time is equal to a difference between the cycle period of the transmissions less a transmission duration of the expected message.

8. The system of claim 1 , wherein acquiring cold start synchronization includes further adapting the microprocessor to: turn on the radio receiver for a limited time to look for the expected message; and if the expected message is detected, to wait for a length of time before turning on the radio receiver to synchronize; otherwise, if the expected message is not detected, to repeatedly turn off the radio receiver for a time asynchronous with the transmission cycle period and to turn it on again until the expected message is detected.

9. The system of claim 8 , wherein the length of time is equal to the difference between the transmission cycle period less the transmission duration of the expected message.

10. The system of claim 8 , wherein the microprocessor is configured to turn on the radio receiver for a limited time to look for an expected message from each transmission source of the plurality of transmission sources.

11. The system of claim 10 , wherein the microprocessor is configured to synchronize to the transmission source of the plurality of transmission sources that has the strongest signal.

12. A method for maintaining synchronization with a periodic transmission from one of a plurality of transmission sources while achieving low power battery operation of a vehicle locating unit in a stolen vehicle recovery system, the periodic transmission occurring during a transmission cycle period and including an expected message that has a transmission duration, the method comprising: using a selectively-actuatable radio receiver of the vehicle locating unit, receiving during periods of actuation the periodic transmissions from the one of a plurality of transmission sources; using a microprocessor of the vehicle locating unit, looking for a synchronization symbol in the expected message and synchronizing subsequent actuation of the radio receiver using the synchronization symbol; reacquiring a warm start synchronization if synchronization is lost; and acquiring a cold start synchronization if the warm start synchronization fails to reacquire synchronization.

13. The method of claim 12 , wherein reacquiring warm start synchronization includes re-checking for synchronization a predetermined number of times; and, if synchronization is not detected, looking for a synchronization symbol after waiting for a length of time.

14. The method of claim 13 , wherein acquiring the cold start synchronization begins if synchronization is not detected after rechecking for the predetermined number of times.

15. The method of claim 13 , wherein warm start synchronization fails to reacquire synchronization if, after the predetermined number of times, loss of synchronization remains.

16. The method of claim 13 , wherein the length of time is equal to a difference between the cycle period of the transmissions less a transmission duration of the expected message.

17. The method of claim 12 , wherein acquiring cold start synchronization includes: turning on the radio receiver for a limited time to look for the expected message; and if the expected message is detected, waiting for a length of time before turning on the radio receiver to synchronize; otherwise, if the expected message is not detected, repeatedly turning off the radio receiver for a time asynchronous with the transmission cycle period and turning it on again until the expected message is detected.

18. The method of claim 17 , wherein the length of time is equal to the difference between the transmission cycle period less the transmission duration of the expected message.

19. The method of claim 17 , wherein turning on the radio receiver comprises turning on the radio receiver for a limited time to look for an expected message from each transmission source of the plurality of transmission sources.

20. The method of claim 17 further comprising synchronizing to the transmission source of the plurality of transmission sources that has the strongest signal.